Nautilus

If you ever have watched through Person of Interest from the first season to the latest season, I beg you have impression on the episode which the Samaritan recruits people on Internet and set up a puzzle solving game for the competitors to solve. That is the second episode of the fourth season, and it is a pretty intense story. A symbol that is used throughout the whole episode is nautilus. 

copy from : Baidu

In that story, the main characters describe the nautilus as a mysterious create: one of natures' many examples of a logarithmic spiral. Isn't this awesome? People can always learn some knowledge from watching TV shows, sometimes the show will introduce some trivial, other times they can teach people some technical terms. Learning knowledge from TV is a big reason I enjoy watching them. So, after I watched the episode repeatedly mentions nautilus, I did some research and explored the secrets of nautilus.

A nautilus shell viewed from above

A nautilus shell viewed from underneath

Nautilus are mollusk animals living since Ordovician Period. Yes, these creature still exist in some oceans in the world. Because nautilus lived for such a long time, they are called as living fossil. Nautilus has unique appearance and shell structure. It’s commonly known that gold ratio and Fibonacci sequence are associated with the spiral shell of nautilus. The spiral shell structure helps nautilus drift and sink in the water. The way nautilus grow its shell is fascinating: “the shell divides into camerae , the chambered section being called the phragmocone. The divisions are defined by septa, each of which is pierced in the middle by a duct, the siphuncle. As the nautilus matures it creates new, larger camerae and moves its growing body into the larger space, sealing the vacated chamber with a new septum. The camerae increase in number from around four at the moment of hatching to thirty or more in adults.” (Wikipedia) The design of submarine actually comes from the function of camerae in nautiluses.

golden number in nautilus (copy from http://www.goldennumber.net/nautilus-spiral-golden-ratio/ ) 

structure of nautilus

Nautilus is a very amazing creature, and there are still many mysteries about these ancient creatures that needed to be answered by the scientists. Because nautilus is such a mysterious creature and can always be related to math, POI choose it as the symbol in that episode.